ZyXEL Communications P-660HNU-Fx User Manual

ADSL Series User’s Guide

The ZyXEL Device can use certificates (also called digital IDs) to authenticate users. Certificates are 
based on public-private key pairs. A certificate contains the certificate owner’s identity and public 
key. Certificates provide a way to exchange public keys for use in authentication. 

• Use  the  Local Certificate screens to view and import the ZyXEL Device’s CA-signed certificates 

(

• Use  the  Trusted CA screens to save the certificates of trusted CAs to the ZyXEL Device. You can 

also export the certificates to a computer (

).

The following terms and concepts may help as you read this chapter.

A Certification Authority (CA) issues certificates and guarantees the identity of each certificate 
owner. There are commercial certification authorities like CyberTrust or VeriSign and government 
certification authorities.

When using public-key cryptology for authentication, each host has two keys. One key is public and 
can be made openly available; the other key is private and must be kept secure. Public-key 
encryption in general works as follows. 

Tim wants to send a private message to Jenny. Tim generates a public-private key pair. What is 
encrypted with one key can only be decrypted using the other.

Tim keeps the private key and makes the public key openly available.

Tim uses his private key to encrypt the message and sends it to Jenny.

Jenny receives the message and uses Tim’s public key to decrypt it.

Additionally, Jenny uses her own private key to encrypt a message and Tim uses Jenny’s public key 
to decrypt the message.